ALT · low result
Low ALT levels: what they mean (and why it is usually nothing)
Short answer
A low ALT — below the lab's lower limit, often under 7–10 U/L — is almost never a medical problem. ALT is released by liver cells, so a low level simply means little enzyme is being released, which is normal for many healthy people and more common in women, older adults, people with small body size or low muscle mass, and in pregnancy. Two situations lower it measurably: vitamin B6 deficiency (B6 is the enzyme's cofactor — alcohol use, poor nutrition, isoniazid, dialysis) and chronic kidney disease, where dialysis patients often run very low values. A low ALT does not indicate liver damage, and there is no treatment for the number itself; in older adults a very low ALT tracks with frailty and low muscle mass, which is the thing worth addressing.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- A low ALT needs no urgent action on its own. Seek care for symptoms, not the number — unexplained weight loss, progressive weakness, or jaundice (which would come with other abnormal liver values).
What is the normal range for ALT?
- Male, age 18+: 7.00 – 55.0 U/L
- Female, age 18+: 7.00 – 45.0 U/L
Full reference table, citations and testing options: ALT biomarker page.
What are the common causes of low ALT?
- Normal variation — many healthy adults run ALT values of 5–15 U/L; the lower limit on most ranges is a statistical boundary, not a disease threshold
- Female sex, older age, and low body or muscle mass — ALT falls with sarcopenia and frailty
- Vitamin B6 (pyridoxine) deficiency — alcohol use, malnutrition, isoniazid, some oral contraceptives, hemodialysis; the assay measures enzyme activity, which needs B6
- Chronic kidney disease and hemodialysis — ALT runs low enough that liver disease can hide behind a 'normal' value in these patients
- Low-protein diets, malnutrition and very low body weight
- Pregnancy — reference ranges are slightly lower, especially in the second and third trimesters
- Smoking — modestly lower values in several population studies
- Laboratory method — assays that do not add pyridoxal phosphate read lower in people who are B6-deficient
What symptoms go with low ALT?
- None — a low ALT itself causes no symptoms
- Any symptoms belong to the cause: cracked lips, a sore tongue, tingling or anemia with B6 deficiency; weakness and muscle loss with frailty; the features of kidney disease
What do clinicians usually check next?
- If you feel well and the rest of the liver panel (AST, alkaline phosphatase, bilirubin, albumin) is normal, nothing further is needed
- Check the other liver values on the same panel — a low ALT with normal AST, bilirubin and albumin is not a liver finding
- Consider a vitamin B6 (pyridoxal-5-phosphate) level when there is alcohol use, dialysis, isoniazid treatment, poor nutrition or unexplained neuropathy
- Kidney function (creatinine and eGFR), since CKD lowers ALT and changes how liver tests should be read
- In older adults, think about nutrition and muscle: protein intake, resistance exercise, grip strength — the correlates of a very low ALT
- Do not repeat the test for the low ALT itself; it will be rechecked with the next routine metabolic panel
Follow-up tests available at TestWell: Vitamin B6 Test (Pyridoxine) ($50.99).
How do you recheck ALT?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| ALT Test (Alanine Aminotransferase) | Test | $16.99 | No | 1–3 business days |
Common questions
Is a low ALT bad?
No. A low ALT means little enzyme is leaking from liver cells, which is the healthy direction. It is common in women, older adults and people with small body size, and by itself is not a sign of any disease.
What does an ALT of 5 mean?
A normal liver that is not releasing much enzyme. In an otherwise healthy person it needs no follow-up. In someone who is frail, on dialysis, drinks heavily or is malnourished, it can reflect low muscle mass or vitamin B6 deficiency, which are worth looking at for their own sake.
Can a low ALT mean liver damage?
Almost never. Damaged liver cells release more ALT, not less. The exception is advanced cirrhosis, where so few working cells remain that ALT can be normal or low — but then albumin, bilirubin, platelets and the clinical picture are clearly abnormal, and the ALT is not the clue.
How is vitamin B6 connected to ALT?
ALT needs pyridoxal phosphate (the active form of B6) to work, and the laboratory test measures activity. In B6 deficiency the measured ALT reads low, which is why dialysis patients and heavy drinkers often have very low values; replacing B6 brings it up.
Why do older adults have lower ALT?
ALT tracks with muscle mass and overall metabolic activity, both of which fall with age. Large studies have linked very low ALT in older adults to frailty and higher mortality — not because the ALT is harmful, but because it marks low muscle and nutrition, which are modifiable.
Should I retest a low ALT?
Not on its own. If the rest of the liver panel is normal and you are well, the next routine metabolic panel is soon enough. Retest sooner only if there is a reason to look at liver, kidney or nutrition for other symptoms.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.